Harman/Kardon HK6850 Amplifier
Having just graduated from the big, black and somewhat-less-than-subtle school of hi-fi design, Harman's original HK6800 has matured into the HK6850 we find here. Unfortunately, maturity does not always herald improvement. So there's still the same rotary selectors for input, rec-out, tape monitor and speaker switching with a comparable subset of controls for bass, treble, balance, MM/MC cartridge selection and 'phase-correct' loudness.
The tone-defeat facility has been retained but HK's video switching and 'main direct' are replaced by a 'Preamp Bypass' option that routes all line-level signals directly to the volume control and power amp. Decent 4mm connections are provided for two pairs of speakers though, once again, these are mechanically switched on a rear-mounted PCB, hardly ideal when you consider this amp can belt-out some 23A of current!
On a more positive note, HK has at last abandoned the '8ohm' and '4ohm' speaker modes of its older amplifiers in favour of a power supply with fixed primary and secondary windings. Saves cash anyway! Otherwise the HK hallmarks of all-discrete MM/MC disc circuitry and a prodigious Toshiba-based power amp retain pride of place.
Sound quality
In perfect accord with its stature as an HK 'super-amp', the HK6850 provided us with an especially deep and powerful sound via its MM phono input. Its bass, in particular, was supremely-defined and one of the strongest in our test, the sort of bass that successfully underpins a marvellous sense of depth and acoustic.
Rachmaninov's Symphonic Dances, according to our listeners, all went 'rather well'. The build-up was packed with anticipation, the explosion of brass handled without a murmur of protest while its reverberation sent a palpable shudder through the soundstage. Every instrument was both detailed and tightly focused though a hint of coarseness, a 'tizziness' marred our full appreciation of Marty Paich's jazz LP.
Reverting to CD brought a similarly smooth and clean balance yet one that was evidently less comfortable with busier passages. Most notably, cracks started to appear in the Prokofiev Symphony, groups of instruments began to harden-up, become congested and eventually caused its broad acoustic to collapse. A pity, because the amp had made simpler passages sound so delightfully effortless and tidy.
Conclusion
By juggling the levels of feedback used in the older HK6800, Harman has influenced the gain and linearity of this version, a simple variation on ^n established theme. So the HK6850 retains the confidence and nimbleness of its forebear, a real treat for devotees of vinyl.
